Apex domains cannot have CNAME records.
Question and response
Question
dig KRSK-SBIT.RU. NS
Answer
KRSK-SBIT.RU. 5 NS ns4-l2.nic.RU.
KRSK-SBIT.RU. 5 NS ns1.KRSK-SBIT.RU.
KRSK-SBIT.RU. 5 NS ns8-l2.nic.RU.
Authority
The response has no authority records.
Additional
ns1.KRSK-SBIT.RU. 5 A 193.105.236.4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0